1. Field of the Invention
This invention relates to integrated apparatus each having a constant speed drive unit and generator unit, and more particularly, to means for obstructing debris originating in one unit from entering the other unit and at the same time permitting fluid communication between the units.
2. Description of the Prior Art
Weight reduction of aircraft components is an important engineering objective which, when achieved, permits an increased aircraft pay load. In recent years, for specified power ratings, substantial reductions in size and weight of aircraft electric generators have been achieved. Much of the size and weight reduction was obtained from integrating a constant speed drive unit and a spray-oil cooled generator unit into a single apparatus with both units sharing a common oil system. High heat transfer coefficients provided by spray oil cooling permitted the size and weight of the integrated apparatus to be reduced and at the same time increase the reliability.
The constant speed drive unit and generator unit had casings which were connected and respectively housed a drive apparatus and generator internals. Integrated drive generator apparatus have, in the past, utilized parallel flow scavenge pumps located in the constant speed drive unit. One pump typically transmitted lubrication-coolant fluid primarily from a point in the generator's casing furthest removed from the constant speed drive unit casing while the second pump scavenged lubrication-coolant fluid from the constant speed drive unit casing and the generator casing portion adjacent the constant speed drive unit's casing. Large openings at the interface between the constant speed drive unit-generator unit enabled evacuation and scavenging of the generator casing's interior by the second scavenging pump. Disposition of both scavenging pumps in the constant speed drive unit facilitated removal and replacement of the generator unit since the number of connections therebetween was minimized and simplified. However, when either unit failed and expelled debris, migration of that debris into the unfailed unit sometimes induced failure of the unfailed unit and caused both units to be removed from service.
Typical constant speed drive units include a pressurizing system which facilitates scavenge pump removal of the lubrication-coolant fluid from the interiors of both units' casings. Inclusion of a solid partition between the constant speed drive unit and the generator unit to prevent debris migration across the interface therebetween would prevent pressurization of the generator casing's interior. Moreover, debris from faulty generator units was sometimes withdrawn from the generator casing's interior into the generator's scavenge pump. Since both scavenge pumps were, heretofore, located in the constant speed drive unit, debris withdrawn from a disabled generator by either pump sometimes disabled the withdrawing pump and thus the constant speed drive unit in addition to the failed generator.
Complete structural segregation of the constant speed drive unit and generator unit was desired for the integrated apparatus while avoiding the use of a second casing pressurizing system. Additionally, debris from a failed unit, if fluidly transportable and sufficiently large to jam the scavenge pump evacuating that unit or of electrically conductive nature capable of short circuiting the generator, should be isolated within the failed unit to facilitate removal of the failed unit and prevent additional apparatus damage.